My S639 would remember the paused position of every single MP3 audio file and MP4 video file only if they were placed in the Podcast folder. There isn't a "bookmark" feature built in to the menu system but the player will remember all of the track's paused positions when they are kept in the Podcast folder.

If you place an MP3 audio file in the Music folder or an MP4 video file in the Video folder, only the last played track will have it's position remembered.

Another benefit of keeping video files in the Podcast folder is that they are listed in alphabetical order with the ability to organize them in sub-folders. If you put them in the Video folder they are listed in order that they were copied to the player. The only downside to putting video files in the Podcast folder is that it won't display the album art (for video files only). But since the album art icon for video files is extremely small this isn't a big deal.

Bottom line:
- Put regular music in the Music directory (last played track's paused position remembered)
- Put audio Podcast in the Podcast directory (all track's paused position remembered)
- Put all videos/movies in the Podcast directory (all track's paused position remembered)
- Don't put anything in the Video directory